As a conventional method of manufacturing a semiconductor device, a method of forming a line and space pattern that has a line width and a space width smaller than an exposure light resolution limit of photolithography method is known. The method is disclosed in, for example, US-2008/0008969 A1.
In accordance with the method of manufacturing a semiconductor device, a line and space pattern of p/6 formed of a first side wall and a third side wall can be obtained on a film to be processed by forming a resist pattern to be the line and space pattern at a pitch (p) of an exposure light resolution limit on the film to be processed, slimming the formed resist pattern so as to have a width of 5 p/6, forming a first side wall so as to have a width equal to an amount of slimming (p/6) on a side surface of the slimmed resist pattern, after removing the resist pattern, forming a second side wall on a side surface of the first side wall so as to have the same width as the first side wall and be formed of a different material from the first side wall in an etching selection ratio, and further forming a third side wall on a side surface of the second side wall so as to have the same width as the first and second side walls and be formed of the same material as the first side wall, and selectively removing the second side wall. The film to be processed is processed by using the first and third side walls as a mask, so that a pattern of 1 p/6 can be formed in the film to be processed.
However, in the conventional method of manufacturing a semiconductor device, since the line width of the film to be processed is smaller than an exposure light resolution limit, it is difficult to form contacts configured to be connected to the pattern of the film to be processed in an upper layer of the pattern of the film to be processed.